1. Field of the Invention
The present invention relates to providing RF-signal coverage for vehicles, and more specifically, the present invention relates to providing RF-signal coverage both inside and outside of an automotive vehicle at the same time.
2. Description of the Related Art
Recent developments in networking and automotive technologies have resulted in the desire to provide RF-signal coverage both inside and outside an automotive vehicle. Various techniques have been attempted to implement RF-signal coverage both inside and outside of automotive vehicles, in particular, to address the problems associated with the bodies of automotive vehicles, which are typically made of metal and thus provide electromagnetic shields that separate the two desired RF-signal coverage areas.
Known methods of providing RF-signal coverage both inside and outside of an automotive vehicle include simply using an RF combiner or an RF switch to split the RF signal into two signal paths: a first signal path for an outside antenna that provides RF-signal coverage outside the automotive vehicle, and a second signal path for an inside antenna that provides RF-signal coverage inside the automotive vehicle. For example, the inside antenna provides a wireless local area network (WLAN) to connect with WLAN-compatible devices inside the automotive vehicle, such as a portable computer, a rear-seat entertainment console, user gaming devices, and the like, or to provide a personal area network (PAN) to connect with PAN-compatible devices, such as a hands-free Bluetooth connection for a cellular phone or other similar device. The outside antenna provides a wireless connection to, for example, WiFi hotspots, access points at residential houses, a dealership service center, and the like.
Although RF switches provide low insertion loss and high isolation between the outside and inside antennas, RF switches permit only one of the outside and inside antennas to be connected at any given time. The outside antenna 101 and inside antenna 102 are typically switched by time division control, for example, of a single-pole double-throw (SPDT) switch 110 as shown in FIG. 6, and overall communication throughput is low because the outside antenna 101 and inside antenna 102 cannot communicate at the same time. That is, relying on an SPDT 110 to combine signal paths to an inside antenna 102 and an outside antenna 101 causes the problem that the inside antenna 102 and outside antenna 101 cannot transmit or receive the RF signals simultaneously.
An RF combiner, or a similar device such as an RF divider or an RF splitter, permits both the outside antenna 101 and inside antenna 102 to communicate at the same time. However, a device 111, such as an RF combiner, divider, or splitter, an example of which is shown in FIG. 7, typically has high insertion loss and low isolation between the outside antenna 101 and inside antenna 102, which reduces signal quality and causes a loss of throughput and a decrease in connection distances. In particular, using such a device 111 to combine signal paths to an inside antenna 102 and an outside antenna 101 results in a high insertion loss to the outside antenna 101, for example, approximately 3.5 dB, and a low isolation between the inside antenna 101 and the outside antenna 102, for example, approximately 3.5 dB.
Furthermore, the above-described methods for providing RF-signal coverage both outside and inside of an automotive vehicle require two different antennas and a substantial length of RF cabling, which leads to high cost and complexity for implementing such methods.
Although known RF radiating cables provide RF-signal coverage for tunnels or buildings, for example, RF radiating cables have not been designed or arranged to provide antennas for automotive vehicle applications.